here are the titles and isbn #s of those watercolor workbooks I suggested:
Basic Watercolor Techniques
edited by Wolf, Albert
Bud Biggs, Lois Marshall
****step by step exercises on trees:
pgs: 14, 22-24, 36-42, and 52-55.
Hope this helps !!!!
Hate to see kids just "fill in" w/o mixing and layering colors at that grade
(whenever there's a sub, that's the kind of "watercolors" I see done ).
Christine in Binghamton